Effect of thermal annealing on light yield,low temperature thermoluminescence,and time profiles of LuAG:Pr scintillator crystals

Measurements of light yield, low temperature thermoluminescence, and scintillation time profiles, performed comparatively on “as grown” and thermally annealed LuAG:Pr samples, are reported. It is shown that traps play an efficient role in the scintillation of LuAG:Pr, being responsible for the yield decrease and introducing a long component to the time profiles. The trap concentrations in the annealed crystals are lower than in the non-annealed ones, which correlates with the yield enhancement.     

Effect of thermal annealing on sub-band-gap absorptance of microstructured silicon in air

The optical absorption properties of femtosecond-laser-made “black silicon” as a function of the annealing conditions were investigated. We found that the annealing process changes the surface morphology and absorption spectroscopy of the “black silicon” samples, and obtained a maximum sub-band-gap absorptance value of approximately 30% by annealing at 1000 °C for 30 min. The thermal relaxation and atomic structural transformation mechanisms are used to describe the lattice recovery and the increase and decrease of the substitutional dopant atom concentration in the microstructured surface during the annealing. Our results confirm that: i) owing to the thermal relaxation, the lattice defects decrease with the increase of the annealing temperature; ii) the quasi-substitutional and interstitial configurations of the doped atoms transform into substitutional arrangements when the annealing temperature increases; iii) the quasi-substitutional and interstitial configurations with higher energies of the doped atoms transform into interstitial configurations with the lowest energy after high-temperature annealing for a long period of time, causing the deactivation or reactivation of the sub-band-gap absorptance by diffusion. The results demonstrate that the annealing can improve the properties of “black silicon”, including defects repairing, carrier lifetime lengthening, and retention of a high absorptive performance.     

Fabrication and photoluminescence characteristic of Pr:LuAG scintillator ceramics

0.5at% Pr:LuAG transparent ceramics was fabricated by a solid state reaction method. The transmission of the ceramics beyond 310 nm reaches to around 75%. When excited by ultraviolet (UV) and vacuum ultraviolet (VUV) light, the domain emission near 309 nm was observed which was due to the 5d–4f radiative transition of Pr³⁺. Its photoluminescence decay time is about 19 ns. VUV excitation and emission spectrum at 14 K and 289 K respectively reveal the existence of defects and other centers, which are sensitive to temperature and anneal process.     

Effect of thermal annealing on spectral properties of electrodeposited carbon films

The effect of thermal annealing on properties of carbon films deposited on nickel electrodes by the electrodeposition method was studied. It has been shown that annealing at a temperature of 300°C results in the formation of nanosize diamond clusters. With an increase in the annealing temperature, the size of diamond clusters diminishes. At an annealing temperature of 900°C, all of the carbon enters into reaction with nickel, thus forming nickel carbide.     

Effect of Mg2+ co‐doping on the scintillation performance of LuAG:Ce ceramics

Ce‐doped Lu₃Al₅O₁₂ optical ceramics co‐doped with Mg²⁺ are fabricated by solid‐state reaction method and further optimized by an air‐annealing process. Mg²⁺ co‐doping leads to a significant decrease of thermoluminescence intensity above room temperature and an increase of scintillation light yield (LY) value and fast component content even if the overall scintillation efficiency decreases. Scintillation LY of ～21900 ph/MeV has been achieved with a short shaping time of 1 μs, and the ratio of LY values for 1 μs and 10 μs shaping times was as high as 79%. The acceleration of scintillation response induced by Mg²⁺ co‐doping and the role of Ce⁴⁺ ions in the scintillation mechanism are discussed.

     

Charge Transfer between Neutron-Induced and Activator Centers in LuAG:Pr Single Crystal

Optics and Spectroscopy - The spectra of absorption and gamma luminescence and integral thermoluminescence curves (300–605 K) of nominally pure LuAG crystals and praseodymium-doped LuAG:Pr...     

Influence of annealing on the scintillation properties of zinc oxide powders and ceramics

It was shown that annealing ZnO and ZnO:Ga initial powders and ceramics in different atmospheres significantly changes the characteristics of the studied samples. Two main luminescence bands of different origins were observed in powders at 540 nm and 580 nm. Annealing either in vacuum or in Ar:H₂ atmosphere increased intensity of green luminescence with peak at 540 nm whereas annealing in air enhanced a luminescence band with peak at 580 nm in the powders. Corresponding changes in luminescence kinetic properties were observed. Annealing of the ceramics in vacuum and air did not affect the luminescence properties, while annealing them in Ar:H₂ atmosphere increased green luminescence intensity of undoped ceramics and excitonic luminescence intensity of doped ones. Comparison of the X-ray, gamma-ray and cathode-ray excited luminescence lead to conclusion that the enhancement of luminescence intensity took place in surface layer of about 100 μm thickness.     

Effect of thermal annealing on optical properties of CR-39 polymeric track detector

The samples of CR-39 polymer (TASTRAK, Bristol, England) were annealled thermally at various temperatures ranging from 100°C to 180°C for 1 hour, in air. FTIR spectroscopy reveals the structural degradation of CR-39 polymer due to thermal annealing above its glass transition temperature. Optical band gap of pristine and thermally annealed samples has been determined using UV-Visible absorption spectra. It has been observed that the optical band gap decreases continuously as a result of annealing.      

Defects in Ce-doped LuAG and YAG scintillation layers grown by liquid phase epitaxy

The single crystalline Lu₃Al₅O₁₂ (LuAG) and Y₃Al₅O₁₂ (YAG) garnet layers doped by Ce³⁺ ions were grown by the liquid phase epitaxy from the flux. The effect of the flux composition, growth conditions, and substrate polishing on the layer morphology, creation of defects, and on optical and emission properties of layers was studied. The defects typical of the epitaxial growth are discussed.     

Electrical and thermal transport properties of dilute Pr in Pd

We have measured susceptibility, electrical resistivity thermopower, thermal conductivity, specific heat, thermal lattice expansion and Hall effect of dilute alloys of Pr (x = 0.014, 0.03) and of Lu (x = 0.014) in Pd. We find a rather strong valence instability at room temperature from L_III X-ray absorption (v = 3.1), which manifests itself by a concentration-independent characteristic temperature, by a resistivity minimum and by a strong anomally of the thermopower. The susceptibility also indicates strong magnetic polarisation of the surrounding Pd-atoms through the excited crystal field levels but not through the ground state of the impurity. The neutron scattering shows several sharp crystal field excitations between 0 and 1 meV and a very broad quasi-elastic scattering at higher temperatures with the 4f-form factor. We take this also as evidence for a weak coupling of valence instabilities to the low lying crystal field levels of the impurity and a strong coupling to the higher ones.     

Effect of thermal annealing on the magnetic properties of thin films of Co-Pd alloys

The results of studies of the effect of thermal annealing on the magnetic properties of thin films of Co-Pd alloys are described, along with a method for obtaining easy-axis perpendicular anisotropy in these materials. The method consists of depositing layers of the alloy on a substrate whose thermal expansion coefficient is considerably smaller than that of the film, and then annealing it in a vacuum. This method is used to prepare samples with rectangular hysteresis loops for magnetization perpendicular to the plane of the film, coercive forces of 750 Oe, and Kerr rotation angles of 0.21°. Also presented are the results of experiments on thermomagnetic recording on the samples. Zh. Tekh. Fiz. 68, 66–70 (April 1998)     

Optical and physicochemical properties of hydrogenated silicon nitride thin films: Effect of the thermal annealing

The effect of thermal annealing on the optical and physicochemical properties of hydrogenated silicon nitride films was studied. These films were deposited by plasma-enhanced chemical vapor deposition from a mixture of silane, ammonia, and nitrogen. Subsequently, the films were annealed at various temperatures ranging from 400°C to 1000°C. The properties of the films were studied using ellipsometry and Fourier transform infrared spectroscopy. The Maxwell Garnet model considers the silicon nitride material as heterogeneous with three distinct phases: silicon, stoichiometric silicon nitride, and hydrogen. Based on the ellipsometric analysis, the annealing treatment leads to reduce the volume fraction of both hydrogen and silicon. As a result, the stoichiometry parameter significantly increases from 1.24 to 1.32 making it closer to the stoichiometric silicon nitride one. According to the infrared data, a noticeable decrease in the total hydrogen concentration in the films was obtained with respect to the annealing temperature.     

Effect of thermal annealing on disorder and optical properties of Cr/Si bilayer thin films

Chromium/silicon bilayers are deposited by sequential electron beam evaporation on quartz substrates. The bilayers consisting of Cr and Si layers of 50 and 400 nm thicknesses, respectively, are subjected to post-deposition annealing at temperatures from 200 to 700 °C. The thermal annealing results in the interdiffusion between Cr and Si, as evidenced by cross-section scanning electron micrographs and the line profiles obtained from energy-dispersive X-ray spectroscopy. It is inferred from the compositional line profiles that the films are a combination of silicon-rich oxide, chromium oxide and unreacted Cr up to 500 °C. Chromium disilicide forms at temperatures greater than 500 °C with decrease in chromium oxide content. The refractive index value and extinction coefficient values are 2.1 and 0.12 in the as-deposited case which increase to 3.5 and 0.24 at 400 °C. These values decrease to 2.1 and 0.12 at 500 °C. At the same temperatures, the band gap values are 2.21, 2.40 and 2.28, respectively. Thus, the refractive index, absorption coefficient and the optical band gap of the films peak at an annealing temperature of 400 °C and decrease thereafter. Significantly, this is accompanied by increase in Urbach energy which is an indication of increase in disorder in the system. There is decrease in Urbach energy as well as the optical constants at temperatures >400 °C.     

热退火对等离子体增强化学气相沉积SiCOH薄膜结构与性能的影响

热退火是多孔低介电常数薄膜制备过程中的重要一环, 对薄膜结构及性能具有重要影响. 本文以四乙氧基硅烷和双戊烯为前驱体, 采用等离子体增强化学气相沉积方法制备了SiCOH薄膜, 对其进行了氮气氛围下的热退火处理, 分析了热退火对薄膜结构与性能的影响, 探究了退火过程中薄膜结构变化的可能的反应机理. 傅里叶变换红外光谱和固体核磁共振谱结果表明, 沉积薄膜是一种有机无机杂化薄膜. 退火过程中, 薄膜中的-CH₂, -CH₃等有机组分被分解除去, 形成了以稳定的Si-O-Si等无机组分为骨架的多孔结构, 并通过氮气吸附/脱附等温线测试得到了验证. 在此期间, 薄膜骨架微结构亦发生一系列调整, C=C, Si-C含量增加, Si、O、C等元素间发生进一步键合. C=C 含量的提高, 使得薄膜的消光系数和漏电流密度增大. 实验证明, 退火后薄膜具有低折射率、低介电常数特性, 是一类具有优异的介电性能和力学性能的材料, 作为芯片后端互连层间介质具有极大的应用潜力.     

Effects of thermal annealing on the properties of N-implanted ZnS films

N-ion-implantation to a fluence of 1×1015ions/cm2was performed on ZnS thin films deposited on glass substrates by using the vacuum evaporation method. The films were annealed in flowing nitrogen at 400?C–500?C after N-ionimplantation to repair the ion-beam-induced structural destruction and electrically activate the dopants. Effects of ionimplantation and post-thermal annealing on ZnS films were investigated by X-ray diffraction(XRD), photoluminescence(PL), optical transmittance, and electrical measurements. Results showed that the diffraction peaks and PL intensities were decreased by N-ion-implantation, but fully recovered by further annealing at 500?C. In this experiment, all films exhibited high resistivity due to the partial dopant activation under 500?C.     

Luminescence and scintillation properties of advanced Lu3Al5O12:Pr3+ single crystal scintillators

In this paper we present the luminescence and scintillation properties of Lu₃Al₅O₁₂:Pr (LuAG:Pr) single crystals with Pr³⁺ concentration of 0.13 wt %, grown by the Czochralski method. The light yield and energy resolution were measured under 662 keV γ-ray excitation. The dominant emission band peaking at 310 nm with a shoulder at 370 nm was observed in the photoluminescence spectrum. High light yield of 24,500 ph/MeV and an energy resolution of 5.3 % were obtained for a 6 × 6 × 2 mm³ LuAG:Pr sample. Light yield dependence on sample height and shaping time was measured. The estimated photofraction in pulse height spectrum and total mass attenuation coefficient at 662 keV γ-rays were also determined and compared with the theoretical ones calculated using the WinXCom program.     

Effect of thermal annealing on nitrogen implanted epitaxial Fe films

Nitridated iron is a promising material for potential applications in permanent magnets. Recent work on stabilization of nitridated iron in a foil form through nitrogen ion implantation and annealing motivates to study effect of thermal annealing on the surface of nitrogen-implanted iron. In this work, we show effect of annealing on chemical state and magnetism of nitrogen implanted epitaxial iron films. It is observed that nitrogen in the lattices only stays at the lower temperatures than 450 °C. In addition, significant reduction and lattice modification are taken placed, when the film is annealed at 450 °C. The increases of saturation magnetization and coercivity, where it is annealed at 450 °C, are likely to be triggered by reduction of oxygen contents at the surface and thinning of Fe₂O₃.     

Galvanic deposition of ZnO nanorods and thermal annealing effects on their optical properties

The effects of NaCl electrolyte concentrations in the range 6-48 mM on the galvanic deposition of ZnO in Zn(Ac)₂ electrolyte is presented. Effects of thermal annealing on their structural and optical properties have been investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) microanalysis and photoluminescence (PL). The results show that the increase of NaCl electrolyte concentration not only results in the increase of the diameter of ZnO nanorods, but also promotes the blue-shift of UV emission of ZnO. After air annealing at 200 °C, 300 °C and 400 °C, the UV emission is first enhanced then quenched sharply, while the visible emission tends to be enhanced tremendously. It can be ascribed to the new defect states introduced in ZnO after annealing at high temperature.     

Effects of thermal annealing on the properties of GaN MSM UV photodetectors

Metal-semiconductor-metal-structured GaN ultraviolet photodetectors have been fabricated on sapphire substrates by metalorganic chemical vapor deposition. The properties of GaN photodetectors have been improved through thermal annealing. With a 3 V bias, the very low dark current is about 200 pA, the maximum responsivity of 0.19 A/W is achieved at 362 nm, and the corresponding detectivity is 1.2×10¹¹ cm Hz^1/2/W. The physical mechanism of the effects of thermal annealing also has been studied.     

Morphological and optical properties of soft-landed supported nanoclusters: effect of rapid thermal annealing

We report the formation of large islands of bi-modal lateral size distributions having one peak at lateral size ～100 nm (height ～70 nm) and another at ～160 nm (height ～110 nm) by soft-landing of size-selected copper nanoclusters (3 nm in diameter) at room temperature (26 °C). Si(100) wafer containing native oxide is used as substrate. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to study the morphological aspects and for optical aspect cathodoluminescence measurement is used. Rapid thermal annealing (RTA) (200 °C, dry N₂, 120 s) induced effects on the morphology shows that individual islands are morphologically stable. A careful qualitative study of the optical property using cathodoluminescence in a SEM before and after the thermal treatment, using RTA, reveals very low diffusion of the cluster material into the substrate.